Back Yster(III)oksied Afrikaans أكسيد الحديد الثلاثي Arabic Óxidu de fierro (III) AST Ferritlər Azerbaijani اوکسید دمیر (III) AZB Дижелезен триоксид Bulgarian ফেরিক অক্সাইড Bengali/Bangla Òxid de ferro(III) Catalan Oxid železitý Czech Eisen(III)-oxid German

Iron(III) oxide

This article is about a red-colored oxide of iron. For other uses, see Red Iron.

Iron(III) oxide
Haematite unit cell
  Fe   O
Sample of iron(III) oxide
Pourbaix Diagram of aqueous Iron
Names
IUPAC name
Iron(III) oxide
Other names
ferric oxide, haematite, ferric iron, red iron oxide, rouge, maghemite, colcothar, iron sesquioxide, rust, ochre
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.013.790 Edit this at Wikidata
EC Number
  • 215-168-2
E number E172(ii) (colours)
11092
KEGG
RTECS number
  • NO7400000
UNII
  • InChI=1S/2Fe.3O checkY[inchi]
    Key: JEIPFZHSYJVQDO-UHFFFAOYSA-N checkY[inchi]
  • InChI=1/2Fe.3O/rFe2O3/c3-1-4-2(3)5-1
    Key: JEIPFZHSYJVQDO-ZVGCCQCPAC
  • O1[Fe]2O[Fe]1O2
Properties
Fe2O3
Molar mass 159.687 g·mol−1
Appearance Red solid
Odor Odorless
Density 5.25 g/cm3[1]
Melting point 1,539 °C (2,802 °F; 1,812 K)[1]
decomposes
105 °C (221 °F; 378 K)
β-dihydrate, decomposes
150 °C (302 °F; 423 K)
β-monohydrate, decomposes
50 °C (122 °F; 323 K)
α-dihydrate, decomposes
92 °C (198 °F; 365 K)
α-monohydrate, decomposes[2]
Insoluble
Solubility Soluble in diluted acids,[1] barely soluble in sugar solution[2]
Trihydrate slightly soluble in aq. tartaric acid, citric acid, acetic acid[2]
+3586.0x10−6 cm3/mol
n1 = 2.91, n2 = 3.19 (α, hematite)[3]
Structure
Rhombohedral, hR30 (α-form)[4]
Cubic bixbyite, cI80 (β-form)
Cubic spinel (γ-form)
Orthorhombic (ε-form)[5]
R3c, No. 161 (α-form)[4]
Ia3, No. 206 (β-form)
Pna21, No. 33 (ε-form)[5]
3m (α-form)[4]
2/m 3 (β-form)
mm2 (ε-form)[5]
Octahedral (Fe3+, α-form, β-form)[4]
Thermochemistry[6]
103.9 J/mol·K[6]
87.4 J/mol·K[6]
−824.2 kJ/mol[6]
−742.2 kJ/mol[6]
Hazards
GHS labelling:
GHS07: Exclamation mark[7]
Warning
H315, H319, H335[7]
P261, P305+P351+P338[7]
NFPA 704 (fire diamond)
[9]
NFPA 704 four-colored diamondHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
0
0
5 mg/m3[1] (TWA)
Lethal dose or concentration (LD, LC):
10 g/kg (rats, oral)[9]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 10 mg/m3[8]
REL (Recommended)
 TWA 5 mg/m3[8]
IDLH (Immediate danger)
 2500 mg/m3[8]
Related compounds
Other anions
 Iron(III) fluoride
Other cations
 Manganese(III) oxide
Cobalt(III) oxide
Related iron oxides
 Iron(II) oxide
Iron(II,III) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Vial with iron(III) oxide
Iron(III) oxide in a vial

Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It occurs in nature as the mineral hematite, which serves as the primary source of iron for the steel industry. It is also known as red iron oxide, especially when used in pigments.

It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturally as the mineral magnetite.

Iron(III) oxide is often called rust, since rust shares several properties and has a similar composition; however, in chemistry, rust is considered an ill-defined material, described as hydrous ferric oxide.[10]

Ferric oxide is readily attacked by even weak acids. It is a weak oxidising agent, most famously when reduced by aluminium in the thermite reaction.

  1. ^ a b c d Haynes, p. 4.69
  2. ^ a b c Comey, Arthur Messinger; Hahn, Dorothy A. (February 1921). A Dictionary of Chemical Solubilities: Inorganic (2nd ed.). New York: The MacMillan Company. p. 433.
  3. ^ Haynes, p. 4.141
  4. ^ a b c d Ling, Yichuan; Wheeler, Damon A.; Zhang, Jin Zhong; Li, Yat (2013). Zhai, Tianyou; Yao, Jiannian (eds.). One-Dimensional Nanostructures: Principles and Applications. Hoboken, New Jersey: John Wiley & Sons, Inc. p. 167. ISBN 978-1-118-07191-5.
  5. ^ a b c Cite error: The named reference atmilab was invoked but never defined (see the help page).
  6. ^ a b c d e Haynes, p. 5.12
  7. ^ a b c Sigma-Aldrich Co., Iron(III) oxide. Retrieved on 2014-07-12.
  8. ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0344". National Institute for Occupational Safety and Health (NIOSH).
  9. ^ a b "SDS of Iron(III) oxide" (PDF). KJLC. England: Kurt J Lesker Company Ltd. 5 January 2012. Retrieved 12 July 2014.
  10. ^ PubChem. "Iron oxide (Fe2O3), hydrate". pubchem.ncbi.nlm.nih.gov. Retrieved 11 November 2020.

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